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At least 289 records · Page 16Linked to original sources
PubMed1981

Regulation of cutaneous previtamin D3 photosynthesis in man: skin pigment is not an essential regulator.

When human skin was exposed to simulated solar ultraviolet radiation, epidermal 7-dehydrocholesterol was converted to previtamin D3. During prolonged exposure to simulated solar ultraviolet radiation, the synthesis of previtamin D3 reached a plateau at about 10 to 15 percent of the original 7-dehydrocholesterol content, and previtamin D3 was photoisomerized to two biologically inert isomers, lumisterol3 and tachysterol3. Increases either in skin melanin concentration or in latitude necessitated increases in the exposure time to simulated solar ultraviolet radiation required to maximize the formation, but not the total content, of previtamin D3. In order of importance, the significant determinants limiting the cutaneous production of previtamin D3 are (i) photochemical regulation, (ii) pigmentation, and (iii) latitude.

Animals↗
PubMed1999

Molecular motors and their role in pigmentation.

Skin pigmentation is orchestrated through a series of complementary processes. After migration of melanoblasts out of the neural crest to epidermis and hair follicle, these cells mature into melanocytes. Differentiated melanocytes produce melanin in specialized organelles, the melanosomes. Moreover, the cytoplasm of melanocytes branches into extensions, the dendrites. Via the tips of these dendrites they donate their mature melanosomes to the keratinocytes resulting in skin pigmentation. Thus, one essential part of the process of pigmentation is the translocation of melanosomes from their site of origin in the perinuclear cytoplasm towards the dendrite tips. Motor proteins are molecules which use the energy derived from ATP hydrolysis to move along cytoskeletal elements, either actin filaments or microtubules, to transport their cargo, which can be organelles, vesicles or chromosomes. This review describes the different classes of microtubule-based and actin-based motor proteins with their characteristics and functional importance in cell biology and organelle transport. Some of them will be highlighted and several recent studies in mammalian pigment cells indicating their role in pigment granule transport will be discussed. As a result of these data and previous suggestions, a model will be proposed for the possible cooperation of both systems in melanosome movement.

Actin Cytoskeleton↗
PubMed2004

Pathology and molecular genetics of the pituitary gland in patients with the 'complex of spotty skin pigmentation, myxomas, endocrine overactivity and schwannomas' (Carney complex).

Carney complex (CNC) is a familial multiple neoplasia and lentiginosis syndrome with features overlapping those of McCune-Albright syndrome (MAS) and other multiple endocrine neoplasia (MEN) syndromes like MEN type 1 (MEN 1). Pituitary tumors have been described in a number of patients with CNC; all have been growth hormone (GH) and prolactin (PRL)-producing. In at least some patients, pituitary gland involvement is manifested by hyperplastic areas; hyperplasia appears to involve somatomammotrophs only and to precede GH-producing tumor formation, in a pathway similar to that seen in MAS-related pituitary tumors (and in oncogenesis in other CNC tissues). One patient with CNC and advanced acromegaly had a GH-producing macroadenoma that showed extensive genetic changes at the chromosomal level. These changes appeared to represent secondary or tertiary genetic 'hits' involved in pituitary oncogenesis and were confirmed at the molecular level. So far, almost half of the patients with CNC have germline-inactivating mutations in the PRKAR1A gene; in their pituitary tumors, the normal allele of the PRKAR1A gene is lost. Loss of heterozygosity suggests that PRKAR1A, which codes for the regulatory subunit type 1alpha of the cAMP-dependent protein kinase A (PKA), may act as a tumor-suppressor gene in pituitary tissue. These data provide evidence for a PKA-induced somatomammotroph hyperplasia in the pituitary tissue of CNC patients; hyperplasia leads to additional genetic changes at the somatic level, which in turn cause the formation of adenomas in some, but not all, patients.

Cyclic AMP-Dependent Protein Kinase RIalpha Subuni↗
PubMed2006

Characterization of OCA2 cDNA in different porcine breeds and analysis of its potential effect on skin pigmentation in a red Iberian strain.

Although the function of the OCA2 gene product has not been totally clarified, variation in OCA2 has been associated with skin and hair pigmentation in human and mouse. However, its contribution to skin colour in domestic species has not been reported. In this study, cDNA and intron 9 sequences of the porcine OCA2 gene have been characterized in several pig populations. The cDNA sequence alignment of 20 animals from eight porcine populations allowed the identification of 10 single nucleotide polymorphisms (SNPs); five of the 10 SNPs were non-synonymous. The intron 9 sequence alignment of 12 animals belonging to four pig populations revealed four additional SNPs. Skin colour variation was analysed in a red strain of Iberian pigs with segregation of three SNPs forming two OCA2 intragenic haplotypes. Results from this study provide evidence of a suggestive dominant effect of haplotypes on colour intensity and indicate an important contribution of additive polygenic effects (h2 = 0.56 +/- 0.21) to the variance of this trait.

Animals↗
PubMed2003

[Characteristics of genetically pigmented skins].

The analysis shows that apart from the relative hyperpigmentation of the "black" skin (genetically determined and variable according to ethnic group, age, sex and solar exposure), which determines the secondary dyschromic reactions to the majority of the dermatosis, and, except the differences of frequency of diseases related especially to geographical or epidemiologic determinisms, there is no true specificity although some entities are little or not described on "white" skin (dermatosis papulosa nigra, acral punctuated hyperkeratosis, progressive macular hypomelanosis of the trunk, acne keloidalis, pseudofolliculitis barbae, aïnhum...).

Humans↗